Characterization of Three Types of Turban Shell Batillus cornutus Muscle—Ultrastructure and Protein Composition

Three types of turban shell Batillus cornutus muscle—foot, opercular and visceral—were examined under an electron microscope, and the results discussed in association with their differences in muscle protein composition. Myofibrils of foot muscle were partially surrounded by a collagen fibril layer of about 1 μm thickness. Diameters of thick filaments fell in a wide range of 22–70 nm (mean value, 50 nm). The myofibrils were found to be crossing each other at right angles. The opercular muscle showed a similar structure, except that the collagen fibril layer was clearly thinner. The visceral muscle which surrounds the viscera was composed of roughly parallel-running myofibrils whose thick filaments had a mean diameter of 50 nm. Paramyosin contents in the myofibrillar protein were 29–41 % through the three types of muscle. The paramyosin to myosin heavy chain ratios were 2.5 and 2.3 in the foot and opercular muscles, respectively, whereas the ratio in the visceral muscle was 1.4. The collagen to crude protein ratio was 45% in the foot, 34% in the opercular and 5% in the visceral muscle, roughly agreeing with their electron microscopic differences.